The present invention generally relates to differentials for motor vehicles and, more particularly, to a limited slip differential employing a magneto-rheological fluid to control operation of the differential.
As is known, many motor vehicles are equipped with driveline systems including differentials which function to drivingly interconnect an input shaft and a pair of output shafts. The differential functions to transmit drive torque to the output shafts while permitting speed differentiation between the output shafts.
Conventional differentials typically include a pair of side gears fixed for rotation with the output shafts and two or more sets of meshed pinion gears mounted within a differential case. However, such conventional differentials have a deficiency when a vehicle is operated on a slippery surface. In particular, when one wheel of the vehicle is on a surface having a low coefficient of friction, most or all of the drive torque will be delivered to the slipping wheel. As a result, the vehicle often becomes immobilized. To overcome this problem, it is known to provide the differential with an additional mechanism that functions to limit or selectively prevent speed differentiation of between the output shafts.
Typically, a friction clutch is incorporated into the differential to provide the limited-slip or non-slip function. In many instances, the friction clutch is a passively-actuated device which limits the differential speed between the output shafts only after a certain differential speed has been met. Additionally, such mechanical devices may not be selectively disengaged during operation of anti-lock braking systems or vehicle traction control systems. For example, four wheel anti-lock braking systems attempt to measure and control the rotational speed of each wheel independently. If a mechanical type limited slip differential is present, independent control of the speed of each wheel coupled to a differential is no longer possible. Accordingly, it would be desirable to provide an improved differential which may be actively controlled in conjunction with other control systems present on the vehicle.